This invention relates to a method of and to a plant for producing biogas and compost.
To produce biogas with fermentable solid organic matter, such as manure, the matter must first go through a methanogenic fermentation, i.e. a fermentation producing methane, the main constituent of biogas. Such fermentation may only occur in an anaerobic (airless and lightless) environment and requires a certain temperature which varies depending on whether the fermentation is to be psychrophile (between 10.degree. and 22.degree. C.), mesophile (between 22.degree. and 45.degree. C.) or thermophile (between 45.degree. and 75.degree. C.). The anaerobic environment is obtained by submerging the organic matter with a liquid. For mesophile fermentation and thermophile fermentation, the required temperature is achieved by heating the mass of matter and liquid with ad hoc means. This may require a considerable input of outside heat thereby correspondingly decreasing the energetic efficiency of the method. This is a long drawn out operation. Further, when the matter is heaped, as is the case with a batch-feed process involving vats, it is difficult if not impossible to achieve appropriate heating of the matter thus leading to inefficient fermentation.